'\" te
.\" Copyright (c) 2001, Sun Microsystems, Inc. All Rights Reserved
.\" The contents of this file are subject to the terms of the Common Development and Distribution License (the "License").  You may not use this file except in compliance with the License.
.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing.  See the License for the specific language governing permissions and limitations under the License.
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.TH ID32_ALLOC 9F "Dec 12, 2001"
.SH NAME
id32_alloc, id32_free, id32_lookup \- 32-bit driver ID management routines
.SH SYNOPSIS
.nf
#include <sys/ddi.h>
#include <sys/id32.h>



\fBuint32_t\fR \fBid32_alloc\fR(\fBvoid *\fR\fIptr\fR, \fBint\fR \fIflag\fR);
.fi

.LP
.nf
\fBvoid\fR \fBid32_free\fR(\fBuint32_t\fR \fItoken\fR);
.fi

.LP
.nf
\fBvoid *\fR\fBid32_lookup\fR(\fBuint32_t\fR \fItoken\fR);
.fi

.SH INTERFACE LEVEL
illumos architecture specific (illumos DDI).
.SH PARAMETERS
.ne 2
.na
\fB\fIptr\fR\fR
.ad
.RS 9n
any valid 32- or 64-bit pointer
.RE

.sp
.ne 2
.na
\fB\fIflag\fR \fR
.ad
.RS 9n
determines whether caller can sleep for memory (see \fBkmem_alloc\fR(9F) for a
description)
.RE

.SH DESCRIPTION
These routines were originally developed so that device drivers could manage
64-bit pointers on devices that save space only for 32-bit pointers.
.sp
.LP
Many device drivers need to pass a 32-bit value to the hardware when attempting
I/O.  Later, when that I/O completes, the only way the driver has to identify
the request that generated that I/O is via a "token". When the I/O is
initiated, the driver passes this token to the hardware. When the I/O completes
the hardware passes back this 32-bit token.
.sp
.LP
Before illumos supported 64-bit pointers, device drivers just passed a raw
32-bit pointer to the hardware. When pointers grew to be 64 bits this was no
longer possible. The \fBid32_*()\fR routines were created to help drivers
translate between 64-bit pointers and a 32-bit token.
.sp
.LP
Given a 32- or 64-bit pointer, the routine \fBid32_alloc()\fR allocates a
32-bit token, returning 0 if \fBKM_NOSLEEP\fR was specified and memory could
not be allocated. The allocated token is passed back to \fBid32_lookup()\fR to
obtain the original 32- or 64-bit pointer.
.sp
.LP
The routine \fBid32_free()\fR is used to free an allocated token. Once
\fBid32_free()\fR is called, the supplied token is no longer valid.
.sp
.LP
Note that these routines have some degree of error checking. This is done so
that an invalid token passed to \fBid32_lookup()\fR will not be accepted as
valid. When \fBid32_lookup()\fR detects an invalid token it returns NULL.
Calling routines should check for this return value so that they do not try to
dereference a NULL pointer.
.SH CONTEXT
These functions can be called from user or interrupt context. The routine
\fBid32_alloc()\fR should not be called from interrupt context when the
\fBKM_SLEEP\fR flag is passed in. All other routines can be called from
interrupt or kernel context.
.SH SEE ALSO
.BR kmem_alloc (9F)
.sp
.LP
\fIWriting Device Drivers\fR
